This invention is directed to hydrocarbyl, particularly alkyl, ethers of sulfur-containing mono- or polyhydroxyl-derived aromatics as high performance/high temperature synthetic lubricant base stocks.
Generally speaking, current synthetic lubricants have a "satisfactory" temperature performance ceiling between about 240.degree. C. to 260.degree. C. in the presence of antioxidants. In the future, the operating temperatures of internal combustion engines and the like are expected to increase in order to boost the engine's efficiency. Polyphenyl ethers, for example, and other hydrocrabon fluids have such higher operating temperatures but are either cost disadvantageous or have limitations on their lubricant properties (such as poor low temp characteristics, for polyphenyl ethers). New base fluids clearly need to be developed.
Sulfurized lubricant compositions are well known in the art. U.S. Pat. No. 4,990,271 is directed to sulfur containing lubricant additives which are useful in providing antiwear, antioxidant and friction reducing properties thereto. U.S. Pat. No. 3,840,463 discloses the use of certain metal dialkyl dithiocarbamates or dithiophosphates in combination with metal-free additives containing sulfur and phosphorous.